Comparative Assessment of Optical Properties of PETG, PU & PETC based Orthodontic Clear Aligners Exposed to a Common Staining Agent: An- InVitro Study

Abstract

Introduction: An increase in non-fixed orthodontic appliance treatment options has been attributed to the growing demand for aesthetic procedures, particularly among adults. As a result, clear aligner therapy was created to treat malocclusion or misaligned teeth. When making aligners, polyurethane (PU) (CA Pro+, Scheu Dental; Iserlohn, Germany) and polyethylene terephthalate glycol (PETG) (Scheu Dental Duran; Iserlohn, Germany) are the most often utilised materials. Recently, a material known as polyethylene terephthalate copolyester (PETC) (Erkodur-al; Pfalzgrafenweiler, Germany) was created. It has great dimensional stability, is viscoelastic, hard, crystal clear, and is break-resistant. To date, no research has been conducted to compare the optical characteristics of PET-C-based materials.

Aims and Objectives: The primary objective was to evaluate and compare the optical properties of PETG, PU & PETC-based aligner material exposed to different staining agents in vitro.

Materials and Methods: The study was carried out on Polyurethane (PU), Polyethylene terephthalate glycol (PETG) and Polyethylene terephthalate copolyester (PETC) based aligner material. A UV-visible spectrophotometric analysis (T0) of the unexposed aligner samples was taken. They were then exposed to a staining agent (black coffee) (Nescafe/ Nestle/ Switzerland) for up to 7 days. Spectrophotometric analysis was done post 7 days (T1) to exposure of staining agent.

Results: After 7 days of immersion, the aligners were washed in an ultrasonic cleaner and measured with a colourimeter. The colour changes (ΔE*) were calculated based on the Commission Internationale de I’Eclairage L*a*b* colour system (CIE L*a*b*), and the results were then converted into National Bureau of Standards (NBS) units. Fourier transformation infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) were conducted to observe the molecular and morphologic alterations to the aligner surfaces, respectively. The three types of aligners exhibited slight colour changes after 12 hrs of staining.

Conclusion: The evidence amassed from this comprehensive investigation underscores the imperative need for further exploration and understanding of the optical characteristics of PETC-based aligner materials. By elucidating the nuances of how different materials respond to staining agents, this study not only contributes to the existing body of knowledge but also informs clinical practices and material selection in orthodontic treatment. Through continued research and refinement, we can strive towards optimizing the performance and aesthetic appeal of clear aligner therapy, ultimately enhancing patient outcomes and satisfaction.